I was you 6 months ago. I now, am SO much better. It gets better but it takes a little work. I think I sat around for a long time trying to decide what to do and wondering if it would just get better on its own.
I developed severe sleep anxiety for 2 months after my girl was born... I could not sleep, I had panic attacks, I thought being a mom was the biggest mistake of my life, I went through a dreary depression.... the list goes on.
It DID NOT get better on its own. I had to bite the bullet and start my medicine... I was a nervous wreck so I did a LOT of question asking and worrying about what was going to happen to my body. To tell the truth, the medicine isn't that bad. I'm sure you've heard or read things that tell you otherwise, but I think it's just rare, anxious people. I spent over an hour at a psychiatrist just asking questions and asking for re-assurance. I can answer a lot of your medicinal questions based on what my psychiatrist says. Medicine only serves as a crutch to recover. You also need to find some type of therapy. There are mental health clinics that take almost all insurances. There are also many great books I can recommend. Therapy was key...
Therapy brought down my anxiety, which in turn, took care of my severe insomnia and then eventually, my depression went away. It was all about the anxiety and anxious feelings. That accounts for SO MUCH of what you are feeling.Once that is in check, everything else will be easier to deal with.
You are a great mom. The fact that you are worried and want help, shows already that you are more than fit to become a parent!

If your baby is new, you still have a lot of time to sort through this.
About your cancer scare, the best thing to do is to go to the doctor. One of the things therapy teaches you is to become a problem solver. How can you solve this problem? How can you calm your nerves about this? Write down ALL of your options. Find a doctor that can listen to your satisfaction. Start going through what you can do
I know it was the worst feeling of my life and I'm here to help!